Process for dewaxing oils



Patented June 7, 1938 UNITED STATES PATENT omen PROCESS FOR DEWAXINGOILS No Drawing.

Application April 10, 1937,

Serial No. 136,180

Claims.

The present invention relates to improvements in the art of separatingwax from wax-bearing oil, such as lubricating oil distillates orresidues. More particularly, the invention pertains to a method in whichcertain materials are added to the wax-bearing oil to condition it sothat the wax may be more readily separated from the oil. The inventionis also applicable to a process for the separation of oil from waxes,such as slack wax, wax cakes, etc. This application is a continuation inpart of our copending application Serial No. 65,414, filed February 24,1936.

Many lubricating oil fractions contain relatively large quantities ofwax which impart a high pour point to the oil and thereby render theseoils less desirable as motor lubricants as they are solid and will notfiow at ordinary temperatures. In order to make these oils suitable foruse at ordinary temperatures, it is necessary to remove the waxcontained in the oil; This is usually accomplished by adding a suitablediluent to the wax-bearing oil, chilling the diluted oil to atemperature sufficiently low to congeal the wax content and thenremoving the wax from the diluted oil by settling, centrifuging, orfiltering.

It is well known that an efficient dewaxing process is one in which thewax may be removed as rapidly as is possible to produce a large amountof dewaxed oil having a reasonably low pour point and to produce a waxreasonably free from oil, that is, having a high melting point. 'Inother words, it is desirable to separate the wax from the oil, forexample, by filtration, at a very high rate and yet to recover as muchwax-free oil as is possible from the original stock. In many of theprocesses now in use, it is possible to produce oils of low pour point;however, the yield of oil recovered is unsatisfactorily low and themelting point of the separated wax is low, indicating that a largeamount of oil is retained in the wax. Also, the rate at which the wax isseparated from the oil by filtration, for example, is also low.

We have discovered that the wax contained in oils may be more readilyseparated by mixing the wax-bearing oil with certain materials whichrender the wax more readily separable from the oil. Hereinafter, thematerials which we desire to employ to condition the wax present in thewax-bearing oil in order to effect more ready separation of the wax fromthe oil will be referred to as wax separation aids.

We have discovered wool grease and lanolin to be quite effective as waxseparation aids in the dewaxing of waxy oils. We have furtherdiscoveredthat oxidized wool greaseand oxidized lanolin to be even more effectiveas wax separation aids than the unoxidized materials. The reason for theunexpected activity of the aforementioned wax separation aids indewaxing oils is not definitely known but it is known that when 5 .asmall amount of either the oxidized or unoxidized material is added tothe oil to be dewaxed,

an improvement is obtained with respect to the yield of dewaxed oil,filter rate, and melting point of the separated wax as compared tosimilar de- 1 waxing conditions when no wax separation aid is employed.One explanation for this phenomenon may be that since the aforementionedwax separation aids contain material amounts of cholesterol andderivatives related to cholesterol, it is possible that such ingredientsare largely responsible for the potency of the aforementioned waxseparation aids.

Wool grease, as is well known, is the grease which naturally protectsthe wool while on sheep 120 or other animals and which amounts to aboutof the fleece. This may be removed from the fleece by scouring thefleece with a detergent solution such as, for example, a soap and sodiumcarbonate solution or by other means utilizing aqg5 hydrocarbon solventsuch as a high test gasoline or naphtha which has no effect upon thewool.

In the latter case, the solution of naphtha and grease is run into astill whereupon the greasy solvent is heated to drive oil the gasolineor. naphtha. The grease which remains in the still is washed with warmwater and dried by blowing with warm air. Wool grease is sometimesreferred to in the United States as degras. The following are theapproximate characteristics of wool grease as recovered by theaforementioned process:

Melting point 97 to 108 F. Moisture content 2 to 2 Ash 0.1 to 0.8% Freefatty acid (figured as oleic acid) About 9 to 10% Saponifiable matterAbout'60% Specific gravity at 60 F .967. Saponification number 113 to123 Acid value Not over 20.9% Viscosity at 210 (Tagliabue) 284 to 292Flash point 372 to 390 F. Fire test 527 to 536 F. Cold test 94 Iodinevalue About 27 In. general, the oxidized wax separation aids may beproduced by subjecting the unoxidized ma- 7 terials aforementioned tothe action of an oxygen,

" or the wasaseparauan in the case of woolgreasej it is preferable todew hydrate the material prior to oxidation;

' The wool grease either chemically treated or "to dehydrated, as thecase may be, is then subjected to oxidation. The conditions and degree ooxidation will vary with the type of material treated. The oxidationconsists in heating the wool grease, for example, to a temperature ofabout 350F. and introducing air, oxygen, ozone 'or hydrogen peroxideinto the charge until suflicient oxidation has taken place to render thematerial active as a wax separation aid and yet retain its compatibilitywith theoil to bedewaxed; In one case,oxidation of a 350 gr. charge ofwool grease was effected by introducing air 'while' maintaining' thecharge at :aliout 340 J F. for 'a'iperiod of about 200,hours whileintroducing air .into the charge at a rate tof. approximately .10 litersper hour. It will be 5 observed however that a 'good'oxidized waxseparationaid maybe produced from wool grease or ,lanolin by oxidizingthe charge under the afore- -m'entioned conditions'for a period between100 to 2600 hours. It .will ;also'be understood that the duration 'ofoxidation may vary depending upon the temperature of oxidation'and therate of air introduction. Withhigher air rates, obviously, *the 'lengthof oxidationmay be materially re duced. I The examples given herein areto be considered merely illustrative and obviously many va'riations'maybe made by those skilledin the art without departing from the spirit ofour invention. 7

The I oxidation reaction with air, oxygen or 40 ozone, or with'hydrogen-peroxide, may be aided when theoxidation reaction iscarriedout in the 1 presence of catalysts' Catalysts which may be employed-withbenefit for this purpose are metal chlorides, such as the chlorides-ofiron, zinc,'tin, aIumi'n'um, metal soaps, such as the naphthenates,oleates, stearates, ricinoleates, p'almitates of sodium, copper,magnesium, aluminum, cobalt andirong T r I fIn carryingiout thedewaxing-process, a small 51) {amount} ile. 0.3%';to 1% by volume of theoxidized or-unoxidia'ed wax separation aid is mixed with or l dissolvedin} the wax bearing' oil, afterwhich the mixture is chilled to asufliciently low temperature to precipitate or solidify the waxcontained 55; in'the oil. The solidified wax may then be separated fromthe chilled-mixture by -settling, cen-, trifuging,-or filtering. Theadded Wax separation aid willbe recipitated'andremoved along withlthe'wax. Ifd'e's'iredfa"encentrated oil solution d may be produced byfirst mixing'or' dissolving a small quantity of the waxy distillate tobe dewaxed with thewax separation aid at an 'leviaa'antennae," such as,for xamp-iyauout 350 F. The concentrated amaria-may her'fbe'added to thewaxy'distillate Qi n anfalnount' 'as to incorporate the desired mountpfth'waisparatiofi a'idtmo the oil to bedewaxed,

Y In'many case s 't rable'tcdildte unmixor wax-bearing o1l andwaxseparation aid j With the chilling step in ordeftd rendr the oil fluidatthe dewaxing temperature; As diluents, we preferably employ liquefied n(rm a1ly fgas sous hydrocarbon such as ='ethane,-'-= ethylene} propane,-propyle'ne," butane,

butylene, or mixtures thereof or we may employ such light hydrocarbonssuch as pentane, hexane, heptane, octane, nonane, or hydrocarbonfractions, such as naphtha, gasoline, kerosene, or gas oil. We may alsoemploy such diluents as acetone, mixtures of acetone and benzol, ethyl,propyl and butyl alcohols, methyl ethyl ketone, diethyl ketone, methylpropyl ketone, ethyl propyl ketone,

cyclohexanone and other ketones, normally gaseous and normally liquidethers, methyl chloride, 19,

dimethyl difluoro-methane, carbontetrachloride, dichlorethylene, ortrichlorethylene, ormixtures h f these hydrocarbons with theaforementioned ydrocarbons. V

' The use of a liquefied normally gaseous diluent, such as liquidpropane, is preferred, since in ad- V 'fditiontoihaving the propertyofretaining less' ;wax insolution at low temperature, it may be employedtoproduce the necessary degree of refrig-V erationtoprecipitate thewax'from the solution 20 by vaporizinga'portion of the liquefiednormally gaseous material from the diluted oil underreduced pressure.

It is thus an object of our invention to improve 'dewaxingcharacteristics of wax-containing oil by 25 adding a small quantity ofan oxidized or runoxidizedwool grease or'lanolin to the oil to .bedewaxed 1 j V A further object of our'inventionresides in'dis Y solvingthe wax-bearing; oil to .be .dewaxedand 30 the aforementioned waxseparationaid in'a suitable diluent, chilling the mixture.tofcongeal'thewax content and separating theicongealed :wax

and oxidized'wax separation aid from'theidiluted oil by filtration,centrifuging or settling. 35

Many'specific objects, features and advantages of our invention willbecome apparent to: those skilledin' the art as the description of ourinven- V tion' proceeds in connection with the specific examples givenbelow which are not to be considered 40' ="as limiting .our inventionbutm'erely. illustrative 0f methods of carrying itout. v In one runabout350 grams ofthefwoolgrease having the characteristics aforementionediwasheated in alstill to a temperature of "about 200 :45 F and was*bl'owngently with' air until approximately theentireimoisturecontentwas distilled from the material. Thereupon, thetemperature I wasincreas'ed'to approximately'34 0 7F, and was-maintainedat such'temper'ature for approximate- 50 Fly 200 hours duringwhich time iairiwas intro- 'duced'into the charge at a rateofapproximately -10 liters perhour. This'"resulted in the produc "tion of-an oxidized wool grease which hadithe followingcharacteristics: f Acid'number 123.0

" The oxidized wool greaseiwas mixed in a;closed ;.'ool

vessel with an" SL1A. E.' 20 waxy lubricating ,oilrdis- I tillate-obtained by the vacuum "distillation" of a of the resultant mixturewas-about"? and 'tl'ie pressure was about 250 lbs. pe'r'square inch Ifheniixture of waxy lubricating oil; propane, and

j oxidizediwool-grease was thenchilled externally; at Iarateoi-approxirnately' 3 E 'per minutezuntil'aijfi temperature ofapproximately 40 F. was. attained, the refrigeration being accomplishedby vaporizing under gradually reduced pressure a portion of propane in ajacket surrounding the chilling vessel. The chilled slurry of propane,lubricating oil and solidified wax and wax modifier was then filteredunder a pressure of approximately lbs. per square inch in order toeffect the separation of the precipitated wax and wax modifier from thechilled propane solution of lubricating oil. The filter rate wasapproximately 16.6 gallons per square foot of filter surface per hourbased on propane-free oil. After distilling the filtrate in order toremove propane, a yield of approximately 84.0% by volume of dewaxed oilwas recovered having a pour point of 5 F. The separated wax had amelting point of about 127 F. as determined by the Ubbelohde method.

The results obtained in the foregoing example indicate that this type ofwax separation aid is quite active in dewaxing oils when it is comparedwith a blank run wherein no wax separation aid is employed. A blank runon the same oil using the same amount of propane and carried out underthe same conditions as above, showed that only approximately 64.8% byvolume of oil was obtained having a pour point of 10 F. The Waxseparated from the oil had a melting point of only 117 F. The filterrate was only 2.4 gallons per square foot per hour. 7

In another run, unoxidized dehydrated wool grease was substituted forthe oxidized wool grease in the above example. The results obtainedindicate that this wax separation aid while not quite as potent as theoxidized material was sufiiciently efiective to warrant its use incommercial dewaxing processes. In this run, the filter rate wasapproximately 11.5 gallons per square foot per hour; the yield ofdewaxed oil was 79.6% by volume with a pour point of 10 F. while theseparated wax had a melting point of about 126 F.

Another run similar to the above but substituting oxidized lanolin whichis a highly refined wool grease showed results as follows: The filterrate was approximately 19.3 gallons per square foot per hour; the yieldof dewaxed oil was 82.2% by volume having a pour point of 5 F. and themelting point of the separated wax was about 127 F.

It will be observed that in the following claims by the term "woolgrease, we intend to include not only the untreated or unrefined woolgrease but also the dehydrated wool grease and also the chemicallyrefined wool grease which is known to the industry as lanolin.

The foregoing description of our invention is not to be considered aslimiting as many variations thereof may be made by those skilled in theart within the scope of the following claims.

We claim:

1. A process for conditioning oils preparatory to the separation of waxtherefrom which comprises mixing said wax and oil with a Wax separationaid selected from the class consisting of oxidized wool grease andoxidized lanolin.

2. A process for separating wax from wax-oil mixtures which comprisesmixing the wax-oil mixture with a wax separation aid selected from theclass consisting of oxidized wool grease and oxidized lanolin, chillingthe mixture to solidify the wax content and separating the solidifiedwax from the oil.

3. A process for separating wax from wax-oil mixtures which comprisesmixing the wax-oil mixture with a wax separation aid selected from theclass consisting of oxidized wool grease and oxidized lanolin and adiluent, chilling the mixture to solidify the wax content and separatingthe solidified wax from the oil.

4. A process as in claim 1 in which the wax separation aid comprisesoxidized wool grease.

5. A process asin claim 1 in which the wax separation aid comprisesoxidized lanolin.

6. A process as in claim 1 in which the wax separation aid compriseswool grease having an acid number and a saponification number similar toW001 grease which has been subjected to oxidation with air for a periodof approximately 200 been subjected to oxidation with air for a periodof approximately 100 to 600 hours at a temperature of approximately 340F. while introducing the air into the wool grease at a rate ofapproximately 10 liters per hour.

9. A process as in claim 3 in which the diluen comprises a liquefiednormally gaseous hydrocarbon.

10. A process as in claim 3 in which the wax separation aid comprisesoxidized wool grease and the diluent comprises a liquefied normallygaseous V hydrocarbon.

CHARLES DOUGLAS BARNES. MARCELLUS T. FLAXMAN.

